Which organelle forms a network of membranes that creates sacs and canals for intracellular transport?

• A. Endoplasmic Reticulum
• B. Ribosomes
• C. Golgi Apparatus
• D. Nucleus

Answer: (A)

The endoplasmic reticulum forms a continuous network of folded membranes that create sacs (cisternae) and interconnected canals throughout the cytoplasm. This system acts as the main transport highway inside the cell, allowing proteins and lipids to move between different compartments. Vesicles bud off from the ER to carry cargo to the Golgi apparatus and elsewhere. The rough ER, studded with ribosomes, specializes in protein synthesis, while the smooth ER handles lipid synthesis and detoxification. In contrast, ribosomes themselves are not a membrane network; the Golgi apparatus is a separate organelle that modifies and packages materials, and the nucleus sits within its own nuclear envelope, not forming the intracellular transport network.